Cook beans and broth on high in slow cooker, covered, 2 hours. Warm oil in pan over medium-high heat. Season chicken with salt and pepper. Cook, skin side down, 4 minutes. Turn and cook for 2 minutes. Transfer to plate; remove skin. Cook onions and garlic in pan, 5 minutes, then stir into cooker with chilies, 1 cup water, cumin and chicken.
Cook on low for 6 hours. Remove 1 cup beans and 1/2 cups liquid; puree and return to cooker. Shred chicken, return to cooker. Spoon into bowls; serve.